1. Field of the Invention
The invention relates to a hydrogen generating device and a control method therefor for generating a hydrogen-rich gas by separating hydrogen from a reformed gas, which is obtained by reforming a predetermined raw material, using a hydrogen separator membrane.
2. Description of the Related Art
A fuel cell, which generates electric power by electro-chemical reaction between hydrogen and oxygen, has recently been gaining attention as an energy source. The fuel cell generates an electromotive force by the electro-chemical reaction between hydrogen and oxygen. The hydrogen to be supplied to the fiel cell is generated by a hydrogen generating device by reforming a raw material, such as hydrocarbon system and the like. In order to improve the purity of hydrogen in the reforms gas obtained by reforming the raw material, a hydrogen separator membrane may be used. The hydrogen separator membrane is a membrane having a permeable property for selectively permeating the hydrogen, and a thin film of palladium or palladium alloy is adopted as such hydrogen separator membrane. When the reformed gas is supplied to one surface of the hydrogen separator membrane, the hydrogen is extracted from the other surface based on a difference of a hydrogen partial pressure, thereby improving the hydrogen purity.
The hydrogen separator membrane has a tendency of becoming fragile or brittle (hydrogen embrittlement) by absorbing hydrogen in a low temperature condition where a proper operation temperature level is not reached. In a conventional hydrogen generating device, such hydrogen embrittlement phenomenon had not been considered. Accordingly, there has been a possibility that the hydrogen embrittlement may occur with the hydrogen separator membrane upon starting operation at which the temperature of the hydrogen generating device is in a relatively low temperature condition. The hydrogen embrittlement may cause cracks or damages on the hydrogen separator membrane.
Further, conventionally when the operation of the hydrogen generating device is initiated in a low temperature condition such as at the time of starting, during a so-called warm-up operation, an uneven temperature rise has occurred within the device and no little thermal stress has been generated in the device. Accordingly, if the hydrogen separator membrane is in a hydrogen-embrittled state, there has been a possibility that such thermal stress may cause cracks or damages on the membrane.